1. Field of the invention
The present invention relates to a milling cutter according to the preamble of claim 1.
2. Discussion of Background
Milling cutters are produced in one-piece or multi-piece construction: smaller milling cutters generally in solid construction, larger milling cutters principally with firmly brazed-in cutting edges or--if possible in terms of design--with interchangeable blades or recently to an increasing extent with indexable inserts. The cutting material used is usually carbide or high speed steel (HSS), occasionally tool steel, oxide ceramics or sintered materials. The so-called shell end mills have proved successful for certain large surface milling work. In general, these milling cutters are produced in HSS-construction and they are preferably helical in the longitudinal direction, since this design operates more smoothly compared with those having cutting teeth arranged parallel to the axis. The shell end mills can start the cut on the work surfaces to be machined in the shape of an end corner, which substantially increases the milling capacity.
It is obvious that the milling cutter wears on both the face side and the peripheral side; regrinding is possible per se, but this operation always requires considerable effort, for the milling cutter must be ground down on the face side in each case by the depth which was in use on the peripheral side. In addition, the individual teeth must then be relief-ground on the face side, which always involves complicated machining which has to be carried out very accurately. These shell end mills can also only be used on one side, for the other head end is designed as a mounting and fixing part, for example having a cotter slot.
In order to avoid these disadvantages a new generation of milling cutters has been developed--the so called indexable-insert cutter heads. These corner face milling cutters with indexable inserts have proved successful for milling work with a setting angle around about 90.degree.. In these milling cutters the resharpening of the blades on tool grinding machines is dispensed with by the use of indexable blades. There is therefore ideal interchangeability where the indexable blades are not brazed but are detachably connected to the basic tool body. The milling cutter must of course meet the requirement for maximum flatness and true-running accuracy in the assembled condition. This requires all individual components such as a basic tool body and clamping and cutting elements to be of the highest accuracy. However, even after these specifications have been complied with, such corner face milling cutters with indexable inserts are only suitable as milling cutters from a certain size of the basic tool body: the cutting elements, i.e. the indexable inserts, their attachment and also their associated chip space require a great deal of peripheral room, so that in small corner face milling cutters only a few cutting elements can be formed on the periphery. This is very disadvantageous in as much as the feed rate, that is the milling capacity depends on the number of cutting edges. If the milling operation has to be carried out with a small feed for this reason, the milling capacity with such a tool remains small per se and therefore uneconomical. But even in the case of large basic tool bodies, in which cutting edges which are sufficient per se could be provided, shortcomings which are reflected in the quality of the milling cutter repeatedly arise in practice when the cutting elements are indexed, despite all individual components being highly accurate.